Employers with 250 or more workers must publish figures on differences in pay between their employees through the Government's gender pay gap service.
Most local authorities in England and Wales submitted figures for the year to March 2022, with around a third of councils already doing so for the latest financial year.
The figures show the median hourly salary for women at Cornwall Council was 8.9% less than for men in the year to March 2022 – meaning women's pay has increased in relative terms, with women earning 10.4% less than men at the organisation in the year to March 2021.
Of the 307 councils that provided data for 2021-22, the average local authority paid women 3% less than their male colleagues – a small improvement from 3.3% the year before.
Data for 2022-23 puts the pay gap at around 2.9% – although only 119 have submitted data so far, with Cornwall Council still to do so.
Jemima Olchawski, chief executive of the Fawcett Society, which campaigns for women's rights, said: "While it's an important step, Gender Pay Gap Reporting isn't a solution on its own.
"As these figures show, there is a gulf between the best-performing and the worst-performing local authorities."
Across England and Wales, 12 councils reported a gender pay gap of more than 20% in 2021-22.
Meanwhile, 88 other councils paid women more than men – with Three Rivers District Council in Hertfordshire reporting a 45% difference.
The number of outsourced employees and differences in the services provided by each council is like to play a role in the variation between them.
Ms Olchawski added urged employers to publish plans on how to tackle their pay gaps, recommending that local authorities share knowledge with those that "need to up their game".
The Local Government Information Unit, a membership body, said councils are moving in the right direction on the gender pay gap – but added there is "more work to be done", particularly in senior positions.
Jonathan Carr-West, the organisation's chief executive, said: “Just 22% of council leaders are women and only 33% of council chief executives.
“With women making up 78% of the workforce across local government, this can have knock on effects across service areas as well as impacting development opportunities for women at all levels,” he added.